In order to suppress degradation of emission during a cold engine operation, a control is discussed in JP2006-329144A, in which a valve overlap period is changed depending on an operation state at the time of an engine start. In this control in a port injection type engine, vaporization of a liquefied fuel adhered on an intake port wall is promoted using a burned gas blowing back to an intake port during the valve overlap period. A temperature of the intake port increases depending on a coolant temperature. Therefore, if the coolant temperature increases as time elapses from the engine start, the temperature of the intake port also increases. In this regard, in the control discussed in the aforementioned document, the valve overlap period is controlled so as to gradually shorten as the coolant temperature increases.